Articles of various types are commonly packaged in wrap-around cartons. In the packaging process, rapidly moving articles and carton blanks are brought together in a packaging machine and the blank is wrapped or formed about the articles while moving through the machine at very high rates of speed. One of the panels of the carton, typically the bottom panel, is formed by overlapping the end portions of the blank and connecting them together by integral locking mechanisms. An example of such an arrangement can be found in U.S. Pat. No. 4,437,606 to Graser, which discloses primary, secondary and tertiary locking elements to connect the panel flaps and prevent them from disengaging. The primary male locking tab is on the outer or overlying flap and engages with a female locking edge in the inner or underlying flap. The secondary locking tab, which guards against withdrawal of the primary locking tab, is connected to the inner flap but overlies the edge portion of the outer flap as it extends into a female locking opening in the outer flap.
The locking arrangement in the Graser patent works well in connection with beverage bottle carriers, or with any carton arrangement in which the panel formed from the overlapping panel flaps is relatively wide. This is because the various locking elements can be properly located and sufficiently spaced apart to allow the flaps and the locking elements carried thereby to be manipulated by the packaging machine into locking engagement. When forming a more narrow carton, however, the same situation does not obtain. In smaller cartons such as those used to package plastic food tubs, the panels are smaller and do not provide as much area in which to locate similar locking elements. Furthermore, due to the tapered shape of may food tubs, the bottom panel of these smaller cartons is often narrower than the top panel, making it even more difficult to provide suitable locking means.
An apparent solution to the problem would appear to merely require reducing the size of the locking elements in order to be able to locate them on the available surface area of the panel flaps. This sould not be satisfactory, howwever, because it would weaken the panel comprised of the connected laps. All other things being equal, smaller locking elements are not able to resist the amount of stress that larger elements can resist. On the other hand, since the basic type of locking arrangement disclosed in the Graser patent has been found to perform well, it would be desirable to be able to use related locking elements in smaller cartons to avoid the need to develop entirely new designs.